Embodiments described herein generally relate to imaging systems, particularly to multi-modality imaging systems, such as Single Photon Emission Computed Tomography (SPECT) and Computed Tomography (CT) imaging systems.
CT imaging systems typically include an x-ray source and a detector. In operation, the x-ray source and the detector are rotated around an object to be imaged such that an angle at which an x-ray beam intersects the object changes. A group of x-ray attenuation measurements, or projection data, from a detector at one gantry angle may be referred to as a “view.” A set of views made at different gantry angles during one revolution of the x-ray source and detector may be referred to as a “scan.” In an axial scan, projection data is processed to construct an image that corresponds to a two-dimensional cross-section or slice of an object being scanned.
SPECT imaging systems, such as Nuclear Medicine (NM) imaging systems, use radioactive isotopes injected into the patient and multiple detectors or detector heads to measure emitted photons to acquire image information using a plurality of detectors. Additionally, in NM imaging systems, the resolution of the detector, such as a gamma detector, is determined by the resolution of the detector (based on the size of pixels of the detector) and the resolution of a collimator attached to the detector. The resolution degrades with distance of the detector, specifically the collimator, from the subject. Thus, the detectors are positioned adjacent to the subject to increase resolution of the NM data.
It can be beneficial to utilize both CT and NM systems to scan a subject such as in known dual-modality imaging systems. In these dual-modality imaging systems separate gantries are typically used. However, having two imaging detector gantries (in tandem) increases the footprint of the system and consequently a larger imaging room or space is needed. Moreover, dual-modality imaging systems that combine the imaging components into a single gantry add complexity to the design and control of the system.
Further, newer CT detectors have an increasingly higher field of view, which increase the CT detector size. The larger CT detector in these dual-modality CT/NM systems results in the NM detector being displaced farther along the examination axis. Thus, the patient travels farther into the bore volume, which can cause claustrophobia and general discomfort for certain patients. In addition, as a result of the increased travel length, the patient table has to be made stronger with additional reinforcements to prevent sagging of the bed as the patient travels through the bore. Further, the increased travel length increases the likelihood the patient may move during the scan creating issues or complexities during registration or alignment between the CT and NM images.